Well, not exactly, GTM makes it easy to slather your site (as much or little of it as you want) with 3rd party js / 1px image tracking pixels. Mostly I see it a

Well, not exactly, GTM makes it easy to slather your site (as much or little of it as you want) with 3rd party js / 1px image tracking pixels. Mostly I see it as a low-code tool to allow the dev team to wash their hands of having to add those manually, but it is certainly possible to hardcode the tags into your templates instead (but then it's a much bigger headache to add and remove them willy-nilly). For tracking your conversions etc. you will often see Google Analytics on a site (and it, in turn, may be installed on the site via GTM... turtles all the way).